Dual channel pumping method laser with metal vapor and noble gas medium

ABSTRACT

A laser pumping method pumps a primary amount of energy into the near red satellite band of a metal vapor and noble gas mixture laser medium and a lesser amount of energy is pumped into a highly excited level to stimulate laser output. The medium is can be a Rb vapor and Xe gas mixture. The lesser amount of energy is pumped into the laser medium to populate an excited level that lies above the upper laser level and transfers atomic or molecular population to the upper laser level by a nonradiative process. In preferred embodiments, the intermediate level is within a few kT of the upper laser level and the primary amount of energy is a large majority of the total energy. A laser device includes metal vapor and noble gas mixture laser medium to populate an intermediate level near an upper laser level, and pumping a lesser amount of energy into a highly excited level to stimulate laser output. The medium can be an Rb vapor and Xe gas mixture in preferred embodiments. A primary energy pump pumps population in a near red satellite band. A second energy pump having substantially less energy than the primary energy pump pumps population to a highly excited level.

PRIORITY CLAIM AND REFERENCE TO RELATED APPLICATION

The application claims priority under 35 U.S.C. §119 from priorprovisional application Ser. No. 61/749,859, which was filed Jan. 7,2013.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with government support under grant no.FA95550-10-1-0456 awarded by the U.S. Air Force Office of ScientificResearch. The government has certain rights in the invention.

FIELD

The field of the invention is lasers. The invention can be applied, forexample, to infrared, visible and ultraviolet lasers, and is suitable tobe used in solid state, gas and liquid lasers. A preferred applicationof the invention is to high-power lasers, e.g. YAG lasers, dye lasers,and to Ti-Sapphire lasers.

BACKGROUND

Generating stimulated emission normally requires that a populationinversion be established between two energy levels (also referred to asstates in the art) of an atom or molecule. Populating the upper laserlevel cannot be accomplished directly from the lower laser level, butrather requires the presence of at least one highly excited levelthrough the pumping process and pump power must flow. Three level lasersystems employ one highly excited level and lasing can occur between twoexcited levels or, alternatively, the lasing transition can terminate atground. FIG. 1A illustrates the principles of a three level system inwhich the ground level of the lasing species is the terminus of thelasing transition.

From a conceptual perspective, three level systems are the simplest inexistence, and provide a convenient example to illustrated laser pumpingtheory. Virtually all three level lasers demonstrated to date (and allcontinuous wave [CW] lasers) have the generalized energy structureillustrated in FIG. 1A. An electrical or optical pump source excites andtransfers atoms (or molecules) from Level 1 (sometimes referred to as alower laser level) to Level 2 (sometimes referred to as a highly excitedlevel). Following a fast, radiationless relaxation of the Level 2population to Level 3 (sometimes referred to as an upper or uppermetastable laser level) by any of a variety of processes (collisions,multiphonon interactions, fluorescence, etc.), lasing occurs on the 3→1transition via a relatively slow transition. Although this simple systemhas proven to be highly successful and provided practically usefuldevices for many applications, it often suffers from several drawbacks.The drawbacks include low quantum efficiency and inefficient relaxationof Level 2.

The quantum efficiency for the laser of FIG. 1A is limited by ΔE, theenergy separation between Levels 2 and 3. A significant difficulty isthat the energy ΔE is dissipated as heat. That is, the fraction:

$\begin{matrix}{\frac{\Delta \; E}{E_{2}} = \frac{E_{2} - E_{3}}{E_{2}}} \\{= {1 - {E_{3}/E_{2}}}}\end{matrix}$

represents the percentage of the energy of every pump photon (assumingthat the laser is optically pumped) that is not recovered in the laseroutput. For a typical three level laser, this percentage is at least5-10%. In many applications, this energy loss not an important concern,e.g., lasers that are pulsed because the laser is “off” much longer thanit is “on.”

High power lasers that are continuous or have a duty cycle (thepercentage of time that the laser is operational) greater than 5-10%,present different problems. In continuous and high duty cycle lasers,the rejection of heat resulting from ΔE in FIG. 1A can be (and generallyis) a serious problem. At a minimum, heating of the laser medium willdistort the output laser beam. In cases where the laser medium is acrystal, catastrophic damage of the crystal can result. Inefficientrelaxation is also another problem. The excitation transfer step(radiationless transition from Level 2 to Level 3) is difficult toimplement as hydrocarbon, which is used to relax the population fromLevel 2 to Level 3, causes pyrolyzing problems that produces “soot” inthe laser.

Efficiently relaxing the population of Level 2 into Level 3 can alsopresent serious engineering issues. For example, three level lasers inthe akali atoms Cs and Rb have been developed that require the use of ahydrocarbon molecule such as ethane (C₆H₆) to relax the population ofLevel 2 into Level 3. However, because the laser medium must be heatedso as to obtain a suitable pressure of the alkali metal vapor, thehydrocarbon will slowly pyrolyze (decompose) as the temperature systemis raised. DPAL (diode-pumped alkali lasers) are a newer class of laserthat pump atomic alkali vapors with diode arrays. See, e.g., Krupke etal, “Multimode-diode-pumped gas (alkali-vapor) laser,” Optics Letters,Vol. 31, Issue 3, pp. 353-355 (2006). In that example, avolume-Bragg-grating stabilized pump diode array pumped Rb vapor. Thelaser operated on the 795 nm resonance D₁ (lasing) transition. Priorwork by Krupke et al. used a titanium sapphire laser as a pump to createpopulation inversions and laser operation on the 795 nm resonance D₁(lasing) transition of Rb. These laser systems also pump the 1→2transition.

Increasing the DPAL lasers to the kW power level and beyond would bedifficult. Various engineering barriers exist. For example, the Rb D₂Linewidth (broadened by ˜1 atm He or ethane)≈10 GHz. Linewidth narrowingis needed with volume Bragg gratings. Electronic stabilization of thediode array wavelength is also required.

The laser transition defines different types of laser system. Inconventional three level systems the laser transition is to ground Level1 (the lower laser level in a three level system). There are also fourlevel laser systems. An example medium that provides four leveloperation is Nd:YAG. In a conventional four level laser, the lasertransition is to a lower laser level slightly above the ground level. Anatural depopulation then occurs to the ground level, and this isanother fast radiationless transition. In the conventional three andfour level systems, the population inversion is achieved in the samemanner. Energy pumps population from 1→2, as shown in FIG. 1A withrespect to a three level laser.

Some lasers are optically pumped, e.g., the DPAL lasers that are pumpedwith diode arrays. The 1→2 pumping transition of FIG. 1A presentsanother potential obstacle to obtaining efficient operation of the lasersystem when the system is optically pumped. In an optically pumpedsystem, the pumping transition from 1→2 suffers from poor absorption.Pump energy is wasted, rendering the laser system less efficient.

Verdeyen, Eden, Carroll, Readle and Wagner U.S. Pat. No. 7,804,877 isdirected toward Atomic Lasers with Exciplex Assisted Absorption. In the'877 Patent, the optical cavity includes a van der Waals complex of analkali vapor joined with a polarizable rare gas. The pair is referred toas an exciplex. An example pair is the CsAr pair illustrated in FIG. 6of the '877 Patent. The generalized pair is illustrated in FIG. 5. Theprimary examples are alkali-rare gas pairs, though mercury and otherpolarizable molecules such as ethane and methane are identified aspossible substitutes for the polarizable rare gas molecule. Thealkali-rare gas atomic pairs are photo pumped in the band known as theblue satellite for the D2 transition of the alkali atom. As a result,the atomic pair is excited (promoted in energy) to the repulsive B stateof the alkali-rare gas diatomic molecule. The rapid dissociation of themolecules in this B state results in populating an excited state of thealkali atom that serves as the upper state for the D2 transition of thealkali atom. A similar process can be used to populate higher-lyingexcited states of the alkali atom. Lasing is obtained on at least twotransitions of an alkali atom without necessity of collision relaxationof one level to the other. Rapid dissociation of the alkali-rare gasmolecule is used to populate the upper laser level. The lasers andpumping method of the '877 Patent use a single pump that is away fromthe atomic resonance on the satellite band. In a transversely pumpedexample of FIG. 11, diodes are on opposite sides of the medium, but thisis for uniform pumping and is in the satellite band.

Efficient operation (or any lasing at all) within the methods of the'877 Patent requires that the separation in energy between the selectedsatellite pump band and laser photons must be greater than, orcomparable to, kT (thermal energy). An example consistent with themethods and systems of the '877 Patent is shown in FIG. 1B which is anabsorption spectrum recorded for a mixture of rubidium (Rb) vapor and Xegas. The optical transmission through a column of this vapor/gas mixtureis given as a function of wavelength in the 755-785 nm spectral region.Absorption increases downward in this graph, and the positions of the D2line of Rb (wavelength of approximately 780 nm) and the blue satelliteof the D2 line of Rb in Xe are also indicated. The energy separationbetween the peak of the blue satellite and the D2 line position is 337wavenumbers (1/cm), or approximately 42 meV, which is 7% greater than kTfor the temperature (473 K=200 degrees Centigrade) at which the data ofFIG. 1B were obtained. Consequently, because the separation between theblue satellite of the D2 line and the D2 line itself is more than kT inenergy, optically pumping the blue satellite results in lasing on the D2line. If the system is pumped closer to the D2 line (for example between765 and 780 nm in FIG. 1B), lasing will not occur.

Most research efforts are directed toward improving the performance oftraditional three and four level laser systems by enhancing theefficiency of the pumping mechanism. It is well known that a populationinversion is necessary to realize a laser, but that direct pumping ofthe upper laser level from the lower laser level (which can be groundlevel or an elevated level) will not yield a population inversionbetween the two levels. Instead, the two levels can be equalized intheory that assumes use of an infinite pump source. Thus, theoryinstructs that a two level system cannot be inverted, i.e., thepopulation of the more energetic of the two levels cannot exceed thatfor the lower of the two levels. With a strong pump source, thepopulations of the two levels can, at best, be equalized. This fails toproduce the population inversion needed for lasing.

SUMMARY OF THE INVENTION

An embodiment of the invention is a laser pumping method. In the method,a primary amount of energy is pumped into the near red satellite band ofa metal vapor and noble gas mixture laser medium and a lesser amount ofenergy is pumped into a highly excited level to stimulate laser output.The medium is an Rb vapor and Xe gas mixture in preferred embodiments.The lesser amount of energy is pumped into the laser medium to populatethe highly excited level that lies above the upper laser level andtransfers atomic or molecular population to the upper laser level by anonradiative process. In preferred embodiments, the intermediate levelis within a few kT of the upper laser level and the primary amount ofenergy is a large majority of the total energy.

An embodiment of the invention is a laser device. The device includesmetal vapor and noble gas mixture laser medium to populate anintermediate level near an upper laser level, and pumping a lesseramount of energy into a highly excited level to stimulate laser output.The medium is an Rb vapor and Xe gas mixture in preferred embodiments. Aprimary energy pump pumps population in a near red satellite band. Asecond energy pump having substantially less energy than the primaryenergy pump pumps population to a highly excited level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A (PRIOR ART) shows the conventional energy diagram thatrepresents laser operation;

FIG. 1B (PRIOR ART) is an absorption spectrum recorded for a mixture ofrubidium (Rb) vapor and Xe gas illustrating a laser system and pumpingin accordance with U.S. Pat. No. 7,804,877;

FIG. 2 illustrates the energy diagram of a laser pumping method of theinvention;

FIG. 3 is a block diagram that illustrates a preferred laser device ofthe invention;

FIG. 4 is a diagram illustrating energy as a function of theinternuclear separation for a Cs—Ar laser medium;

FIG. 5 is a plot illustrating a broad red shoulder (satellite) availableto pump as a primary pumping band in a method of the invention in aCs/Kr/C₂H₆ laser medium;

FIG. 6 illustrates a thermally mixed level that can be pumped as theprimary pumping band in accordance with the invention for a K-rare gaslaser medium;

FIG. 7 is an absorption spectrum (relative transmission v wavelength)for a mixture of rubidium (Rb) vapor and Xe gas illustrating a lasersystem and pumping in accordance with an embodiment of the inventionhaving dual energy (channel) pumping bands; and

FIG. 8 is an absorption spectrum (transmission intensity v wavelength)for a mixture of rubidium (Rb) vapor and Xe gas illustrating a lasersystem and pumping in accordance with an embodiment of the inventionhaving dual energy (channel) pumping bands.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of the invention is a laser pumping method. In the laserpumping method of the invention, a primary pump populates anintermediate level that is near (measured by thermal energy) of theupper laser level (Level 3 in FIGS. 1 and 2). The primary pumppreferably delivers a large majority of the total pump power to anintermediate level that lies within a few kT (where kT is the thermalenergy) of the laser level. A secondary pump pumps significantly lesspower to a level (a level from which a fast transition occurs to thelaser level—Level 2 in FIGS. 1 and 2) that is an excited level above theupper laser level (corresponding to a conventional highly excitedlevel).

The invention directs most power toward pumping to the intermediatelevel that exists near the upper laser level (within a few kT) in alaser medium that supports the intermediate level. In methods of theinvention, most of the available pump power is devoted to driving a twolevel system, but a second weaker pump is directed toward populating theupper laser level by another route. The second, weaker pump inducesstimulated emission on the desired transition (rather than thetransition driven by the strong pump) and is thus able to drive thesystem over threshold, producing lasing. Without the secondary pump, thestrong pump alone will produce no lasing on the desired transitionbecause the strong pump alone would be driving a two-level system. Thisalso provides a control method that can use relatively small amounts ofenergy to switch the laser via control of the secondary pump.

Methods of the invention contradict the manner in which three (and four)level lasing systems have been pumped for the past 50 years. However,methods of the invention can produce more efficient lasers of higheraverage power than known lasers.

Preferred embodiments of the invention provide large pump acceptancebandwidths, typically >5 nm, while avoiding the need for diode binning,line narrowing and phase locking.

Preferred embodiments of the invention will now be discussed withrespect to the drawings. The drawings may include schematicrepresentations, which will be understood by artisans in view of thegeneral knowledge in the art and the description that follows. Featuresmay be exaggerated in the drawings for emphasis, and features may not beto scale.

Example embodiments use an optically pumped system. The primary pump andsecondary pump are then realized with two different wavelengths, e.g.,two colors.

A method of the invention is illustrated in FIG. 2 for a three levellaser of the invention. Level 1 is the ground level, Level 2 is anexcited level from which population is typically transferred to upperlaser level 3 by a nonradiative process. The intermediate level 4 lieswithin a few kT of the upper laser level 3. While shown below the upperlaser level 3, it can also be above upper laser level 3. When theintermediate level 4 is below the upper laser level 3, then cooling ofthe laser medium is provided as an additional benefit. This represents aparticularly preferred embodiment, and is especially advantageous forhigh power lasers.

FIG. 3 is a block diagram showing an optically pumped laser system ofthe invention that can implement the method of FIG. 2. In the system ofFIG. 3, a first optical pump 10 that pumps to intermediate level 4 and asecond optical pump 12 that pumps to level 2. Energy is pumped into alaser medium 13, e.g., a gas laser medium or a crystal. Mirrors 14create feedback, and a lens 16 focuses and exit laser beam 17, which canbe a high power beam (e.g., tens of Watts to hundreds of or greater andinto the kW range and multiple kW weapons power ranges). The radiation18 from pump 10 will have a first predetermined wavelength, and theradiation 20 from pump 12 will have a second predetermined wavelength.The wavelengths will depend upon the medium. The primary pump 10 has thebulk of the power, as controlled by a controller 24. The primary pump 10populates the energetic Level 4 in FIG. 2. The secondary pump receives asmall amount of power, but populates energetic Level 2, and is necessaryto create a population inversion for lasing. The controller 24 cantherefore use the secondary pump as a fast switching control. Theoperation can be well understood by artisans with reference in FIG. 2.

FIG. 3 illustrates a transverse pumping arrangement, but axial pumpingarrangements are also possible. An example axial pumping arrangement isshown in FIG. 10 of Verdeyen et al., U.S. Pat. No. 7,804,877, which isincorporated herein. The FIG. 10 configuration of the '877 patent can bemodified with a second pump diode directed toward the primary pump bandof FIG. 2 in the present application to populate energetic Level 4.

In FIG. 2, Level 4 lies slightly above or below the upper laser level(Level 3). Levels 3 and 4 can be considered thermally mixed, andeffectively act in some respects as a single level. The energyseparation between 3 and 4 is ΔE′ which is on the order of thermalenergy (a few kT) or less. Not only is Level 4 in proximity to Level 3but a laser medium supports that level 4 can be pumped efficiently fromLevel 1. Advantageously, this implies that the absorption coefficientassociated with the 1→4 transition in FIG. 2 is large. This contrastswith the traditional weak 1→2 transition.

In preferred embodiments, optical pumping is used, as illustrated inFIG. 3.

Two different wavelengths (channels) of pumping light provide a “twocolor” approach. Most of the power is delivered to the laser medium bythe “Primary Pump.” For example, in one embodiment, 90% of pump power isprovided to the primary pump, and 10% to the secondary pump. Thiscontrasts with typical lasers, where all pump power is devoted towardpopulating Level 2. In the invention, the burden of populating theintermediate level 4 that is proximate the laser level 3 is carried bythe primary pump as illustrated in FIGS. 2 and 3. Considerably lesspower is delivered to the laser medium by the secondary pump whichdrives the 1→2 transition.

The method of FIG. 2 can be much more efficient than typical pumpingcompared to the conventional pumping of FIG. 1A, and especially in thecase of high power lasers. With the intermediate level 4 being within afew kT of the laser Level 3, the population of Level 4 is veryefficiently transferred to Level 3 by collisions (for a gas phase laser)or photon interactions (in a solid). Therefore, when lasing begins,energy stored in Levels 3 and 4 will be extracted efficiently.

FIG. 2 illustrates a preferred embodiment that uses a laser medium thatsupports and pumps to a Level 4 that is ΔE′ below upper laser Level 3.Other embodiments use a laser medium that supports and pumps to a Level4 that is ΔE′ above upper laser Level 3.

The preferred embodiment of FIG. 2 provides an important additionaladvantage. Because Level 4 lies below Level 3 (in the embodiment of FIG.2), lasing on the 3→1 transition will actually cool the laser mediumslightly. That is, each laser photon emitted by the medium removes ΔE′in energy, thereby lowering the medium temperature slightly. This is anenormous asset for high power lasers (>tens of watts). Conventional highpower lasers have significant cooling problems that generally increasewith higher pumping levels. The method of FIG. 2 dramatically reducesthe dependence upon the 1→2 pumping transition and its well-known poorquantum efficiency.

Additionally, the 1→4 transition is that the quantum efficiencyassociated with pumping the 1→4 transition can be, for example, 90% tomore than 100%. The system requires the secondary pump. Lasing is notnormally obtainable on the 3→1 transition when pumping on the 1→4transition alone because levels 3 and 4 are essentially degenerate. Theprimary pump can drive the system to the threshold of lasing (basicallyclose to or at optical transparency), and the secondary pump drives thesystem over threshold. Advantageously, the strong →4 transitionpopulates Levels 3 and 4 efficiently while simultaneously cooling thelaser medium. Levels 3 and 4 are effectively mixed because energyseparation between 3 and 4 is ΔE′ which is on the order of thermalenergy (a few kT) or less.

The laser medium used must provide level 4. Atomic and molecular systemscan provide level structure of FIG. 2, and some have been used inspectroscopy. The invention can, for example, provide high, power lasersin both gas and solid state systems. As a specific example, alkali-raregas diatomics are well-matched to the FIG. 2 energy diagram.

Preferred embodiments are atomic lasers by the dissociation of analkali-rare gas complex, such as Cs—Ar and Cs—Ar—Xe mixtures. FIG. 4 isa diagram illustrating energy as a function of the internuclearseparation for Cs—Ar. A level 2 normal pump band λ_(P)˜837 nm is and thelaser level 3 (metastable level) at λ_(P)˜852.1 nm. In the invention, aprimary pump is pumped within a broad red shoulder of the D₂ transitionthat is available in the 852-854 nm range. The shoulder is illustratedin FIG. 5. The Red shoulder strongly populates Cs (6 ²P_(3/2)) Level (D₂line upper level). FIG. 6 illustrates a thermally mixed Level that canbe pumped with the invention. Pumping can be on the D₂ line or regionbetween D₁ and D₂ transitions. There is a Rapid 4 ²P_(1/2)→4 ²P_(3/2)transfer (ΔE=57 cm⁻¹).

One particular embodiment of the invention is an improvement of thelaser system of FIG. 1B. An objective of the present invention isproviding lasing efficiently while still pumping a state lying within kTof the upper laser level. FIG. 7 illustrates such a system. Theabsorption spectrum is similar to that of FIG. 1B (for a mixture ofmetal vapor and noble gas, in particular an embodiment with Rb vapor andXe gas) but recorded over the 775-798 nm region. Transmission of 1.0corresponds to no absorption by the metal vapor/gas mixture. Thespectrum of FIG. 7 does not completely and accurately represent the RbD2 and D1 absorption profiles because absorption at these wavelengths(780 and 795 nm, respectively) is clearly saturated. A more accurate(unsaturated) absorption spectrum for the Rb—Xe system in thiswavelength region is shown in FIG. 8. The purpose of FIGS. 7 and 8 is toindicate the positions and spectral widths of the red satellitesassociated with the D1 and D2 lines of an alkali atom (Rb, in this case)in an alkali-rare gas mixture. Artisans will note, for example, that thewidth of the D2 red satellite (determined by deconvolution from the D2line profile itself) is roughly 1 nm. Such a width allows for opticalpumping with semiconductor diode lasers without the requirement forline-narrowing. One particular embodiment uses the of this invention isto photopump as the primary pump, for example, the D2 red satellite thatpeaks at approximately 781.4 nm and also pump, as the secondary pump,the blue satellite (760 nm) simultaneously in order to obtain lasing onthe Rb D2 line at 780 nm. With the invention, pumping the D2 redsatellite with the majority of pumping power populates a state lyingbelow the upper state for the D2 line. Every photon absorbed at 781.4 nm(red satellite) that also produces a laser photon at 780 nm andadvantageously results in a slight cooling of the medium.

With reference to FIG. 7, another embodiment of the invention isachieved by primarily photo pumping the D1 red satellite and secondarilyphoto pumping one of the D2 red satellite, the D2 blue satellite or theD2 line directly, which obtains lasing on the D1 line (795 nm). Theprimary amount of the required pump power is delivered into the red D1satellite which, if pumped alone, would not result in lasing on the D1line of Rb.

Artisans will recognize that the examples provide guidance for theselection and testing of particular laser media that can provide thenecessary Level 4 to implement the invention. Artisans will recognizethat other laser mediums can be used and support the invention.

Testing is expected to reveal, for example, that tens of watts at 852.1nm or 894.3 nm in the near-infrared can be generated with the inventionwhen Cs—Ar—Xe mixtures are pumped by semiconductor laser bars. Combinedwith frequency-doubling, this laser is modeled to yield more than 10watts of violet (426 or 447 nm). This is a region of the spectrum forwhich few powerful sources exist. This can be provided in a compactphysical form, having a volume of less than about 1 ft³. This laser iswell-suited for many applications, examples of which includephotochemical processing, displays (used to pump RGB sources) anddigital optical disk mastering. The invention is also applicable to highvalue solid state lasers, such as the Nd and Er systems. In suchsystems, the invention can reduce thermal loading of the crystal. Inconventional Nd, Er and other solid state systems, thermal loading is animportant performance limiting issues that causes distortion in thespatial profile of the laser beam.

While specific embodiments of the present invention have been shown anddescribed, it should be understood that other modifications,substitutions and alternatives are apparent to one of ordinary skill inthe art. Such modifications, substitutions and alternatives can be madewithout departing from the spirit and scope of the invention, whichshould be determined from the appended claims.

Various features of the invention are set forth in the appended claims.

1. A laser pumping method, comprising photo pumping a primary amount ofenergy into the near red satellite band of a metal vapor and noble gasmixture laser medium to populate an intermediate level near an upperlaser level, and pumping a lesser amount of energy into a highly excitedlevel to stimulate laser output.
 2. The method of claim 1, wherein thelaser medium comprises Rb vapor an Xe gas mixture, the near redsatellite band comprises the D1 satellite band, and the highly excitedlevel comprises one of the blue satellite band, D2 red satellite, the D2blue satellite or the D2 line directly of the Rb vapor an Xe gas mixturelaser medium.
 3. The method of claim 2, wherein the primary amount ofenergy brings the medium close to lasing threshold and the secondaryamount of energy produces a population inversion between the upper laserlevel and a lower laser level.
 4. The method of claim 2, wherein theprimary amount of energy pumps at ˜781.4 nm and the lesser amount ofenergy pumps at ˜760 nm to achieve lasing on the Rb D2 line at 780 nm.5. The method of claim 2, wherein the primary amount of energy pumps at˜781.4 nm and the lesser amount of energy pumps at one of the D2 redsatellite, the D2 blue satellite or the D2 line directly, to achievelasing on the D1 line (795 nm).
 6. The method of claim 2, wherein theprimary amount of energy delivered by the primary pump is a largemajority of the total pump power delivered by the primary amount ofenergy and the lesser amount of energy.
 7. The method of claim 2,wherein the primary amount of energy comprises ˜90% of the total pumppower.
 8. The method of claim 2, further comprising controlling thelesser amount of energy to switch a laser output on and off
 9. A laserdevice, the device comprising: a metal vapor and noble gas mixture lasermedium; a primary photo pump pumping energy into a near satellite bandof the laser medium; a second photo pump for pumping, with substantiallyless energy than the primary energy pump a highly excited level.
 10. Thedevice of claim 9, wherein the laser medium comprises Rb vapor an Xe gasmixture, the near red satellite band comprises the D1 satellite band,and the highly excited level comprises one of the blue satellite band,D2 red satellite, the D2 blue satellite or the D2 line directly of theRb vapor an Xe gas mixture laser medium.
 11. The device of claim 10,wherein the primary photo pump pumps at ˜781.4 nm and second photo pumppumps at ˜760 nm to achieve lasing on the Rb D2 line at 780 nm.
 12. Thedevice of claim 10, wherein the primary photo pump pumps at ˜781.4 nmand the second pump pumps at one of the D2 red satellite, the D2 bluesatellite or the D2 line directly, to achieve lasing on the D1 line (795nm).
 13. The device of claim 10, wherein the primary and second photopumps comprise laser diodes, the device further comprising a controllerfor controlling the primary and secondary photo pumps, mirrors to createoptical feedback and a lens for outputting a laser beam.
 14. The deviceof claim 10, wherein the primary photo pump and the secondary photo pumpdelivery optical energy transversely to a lasing direction of thedevice.
 15. The method of claim 10, wherein the primary pump delivers alarge majority of the total pump power delivered by the primary andsecond energy pumps.
 16. The method of claim 15, wherein the primarypump delivers ˜90% of the total pump power.